Knots

Knots

Knotty boards are beautiful, yet frustrating! Here's how to get the most out of them.

by Tom Caspar

Knots are usually considered defects in wood. They’re cut out of boards and thrown on a scrap heap. But take a closer look at a knot. In a hardwood, it’s surrounded by stunning grain. Why not make it the focal point of your next project?

The best knots crop up on some of the least expensive, lowest grade boards available. Dealing with knots can add extra work to a project, but you don’t need any special equipment. You just have to know what you’re up against. To begin, take a look at where the three basic types of knots come from in the photos at right.

An intergrown knot is the base of a living branch within a tree. It’s surrounded by a halo of circular growth rings. An intergrown knot is also called a “tight” knot because it’s tightly bound to the wood around it.

An encased knot is formed when a tree grows around a dead branch. It’s surrounded by a dark ring of bark, and its center is often decayed. An encased knot is also called a “loose” knot, because the bark prevents the knot from tightly binding to the wood around it.

A spike knot is formed when a board is cut right through the length of a branch. A spike knot may be tight at its base (the intergrown portion) and loose at its end (the encased portion).

Use knots for drama. Here’s an opportunity to have fun with unusual patterns, as in this spalted-maple kitchen table. It has a comet-shaped pairing of a huge intergrown knot and a very long spike knot. Showing off the incredible swirling grain around a knot turns an inexpensive, lower grade board into a beautiful example of nature’s art.

Resawing can be spectacular! A board with knots near an edge yields the most interesting mirror-image patterns, as shown in this piece of aromatic red cedar. Before you cut a board down its length on a bandsaw, hold the board on edge against a mirror. The outside of the board and its reflected image give you a pretty good idea of the book-matched pattern you’ll get after resawing.

Keep your distance from knots when you’re cutting them out. It’s tempting to get the last inch out of every clear piece, but often it’s not worth it. The wood fibers around a knot have a very steep slope. (Right next to the knot, they run almost vertically, the same direction as the branch grew on the tree.) Wood fibers with a steep slope are called “short grain.” Short grain weakens the end of a board, making it unsuitable for rails and legs. Short grain may also cause the end to chip out when you joint or plane the board.